MA Audio HK602SX

[mike49504]

I replaced the outputs in this amp and its still stuck in protection mode.

Heres what i have on the 494

1:10.36
2:3.11
3:4.76
4:0.05
5:1.48
6:3.43
7:0
8:13.91
9:0
10:0
11:13.91
12:12.54
13:4.98
14:4.98
15:4.77
16:0

 

[Perry Babin]

Post the DC voltage on the op-amp near the 494.

IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

 

[mike49504]

NJM2904L

1:0
2:8.54
3:2.55
4:0
5:9.02
6:4.98
7:11.06
8:12.53

 

[Perry Babin]

If there is a PNP transistor with it's collector connected to pin 5 of the op-amp, pull it. Does the amp power up?

Be careful, the amp may draw excessive current.

 

[mike49504]

Ok theres 3 transistor in the power supply section 2 C102's and B631K pulled 1 at a time amp still is in protection

 

[Perry Babin]

Did any of those have their collector connected directly to pin 5?

 

[mike49504]

ON the C102 transistors do you know which leg is the collector I cant seem to find a datasheet on theese

 

[Perry Babin]

I think the pin configuration is ECB.

 

[mike49504]

none of them had the collector directly connected to pin 5 . The 3rd leg of the C102's connected through resistors then to pin 5

 

[Perry Babin]

I'm using the 802 as a reference so it may be a bit different. Is there a diode with its anode directly connected to pin 1?

If so, reinstall any parts from this area that are out of the circuit and desolder one leg of that diode. That should defeat the protection circuit so you can determine if the fault is in the audio circuit or in the protection circuit.

 

[mike49504]

There are 2 didoes that connect to Pin 1 Both anode side ( non stripped side)

They are D22 D23 Do i unsolder 1 at a time?

 

[mike49504]

Ok unsoldered both of them . Amp is still in protection mode

 

[Perry Babin]

Post a photo of this area of the board.

 

[mike49504]

I have everything in the board and solderd back together at this point.

Heres a pic of the power supply area

 

[Perry Babin]

D24 at the end of the the 494 is the one I need you to pull.

 

[mike49504]

Ok Now amp draws excessive current when trying to power up

 

[Perry Babin]

If it's out of the sink, power it up for just a few seconds. Which of the output transistors get hot?

 

[mike49504]

They remain cool Only thing thats heating up is the power supply fets

 

[Perry Babin]

Power supply problems can't cause the amp to go into protection. Measure the DC voltage across the emitter resistors. You'll have to have it out of the sink. If the PS FETs are heating up, you'll have to place the probes across each of the resistors, and note the voltage at the point where the amp begins to draw excessive current, power down, move the probes and do it again. You'll have to measure accurately. None should read greater than 0.000v DC.

I'm assuming that you've check the drivers and outputs already.

 

[mike49504]

I checked all outputs and drivers the problem is in the left channel.

Heres what i get on the drivers for the outputs:

D600K

1-2:OL
1-3:0.596
2-3:0.594

probes reversed

1-2:OL
1-3:OL
2-3:OL

I get the same readings on both D600K's

B631K

1-2:OL
1-3:OL
2-3:OL

Probes reversed
1-2:OL
1-3:0.606
2-3:0.601

I get the same reading on both of thoose.

Thoose appear to look good.

All outputs were taken out of the board and tested for shorted/leaking all test the same and appear to be good.

Wondering where i go from here?